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After Bebe80 suggested using a Max4410 as an amp for another project, it got me to thinking about my idea of a aux hearing aid device for high sweat conditions (hearing aids are $5k per pair and sweat really knocks them out)
Plan is to use ear buds with a MAX4410 as amp, MAX5408 as a digital potentiometer and throw in a band pass filter. Using a PIC to control the max5408 which uses SPI for control.Have a noise canceling circuit or ? using the PIC to control volume upon loud noises.
This is just in the thought process but on the back burner.
Any suggestions as to implementing this idea?.
I don't sift through the forums often, but this thread caught my attention. I thought of using DSP's to accomplish the same technique, even before I knew this thread existed. After thinking it over, I thought it would be very helpful for those who work in noisy applications. For example, I've noticed that many workers on job-sites, with electric saws, air guns, and other noise-making products impede hearing sensitivity over time. With something like this, workers could select the frequencies at which the products produce noise, reject them, and still be able to talk with other workers perfectly. The difficulty would be contriving two minuscule hearing aids while having extended battery life.
My present hearing aids have two mics per unit which are programmable depending on environment.
My idea is to have a small battery pack(the components I am thinking of using are 3v with up to 7ma current draw. Hopefully a max of 10ma which would last several weeks and possibly be rechargeable.
As for size of unit, The ear buds as used for Ipods etc would be utilized as a cost saving measure. My projected cost is under $30 complete.
Sweat moisture, heat etc are the determent to hearing aids but this proposed unit would not(hopefully not) be affected.
Yes I know about the sonic ear units as advertised on tv. This would be similar BUT have noise canceling, bandpass filters etc. Using a PIC would control all the different functions.
Using an array of mics mounted on a necklace under the clothing similar to https://www.electro-tech-online.com/custompdfs/2010/10/j2001amicrophone.pdf
I hope I got the correct link.
The unit could possibly be programed for various noisy environments (hunting, hammering, banging, loud engines etc)
This is just in the planning stages. may or not even get built but maybe it will all come together. I have the headphones, 2- max4410 amps, the PICs. mics are on the shelf at electronic goldmine at a reasonable cost. A sample of the max5408 needs to be ordered but want to do more research on the use of digital pots.
Found by adding pots I can increase the bandwidth. Plan is to use a digital pot to control bandwidth according to hearing abilities.
use a PIC to control the pots and a MAX4410 80mw stereo headphone driver with shutdown
don't really know what I am doing but simulating with TINA for opium results. Audioguru suggested a wider bandwidth the orginal speech filter was 250hz - 2700hz
Using pots set at pictured settings I am able to widen the bandwidth to 294hz-8100hz
tweaking I could maybe get the low end lower?
hopefully going in the right direction?
Maybe someone with more knowledge about this subject like Audioguru can offer suggestions.
using the ADC input on the PIC I think it can be utilized to shut off LOUD noises?
We discussed audio filters before but I can't remember.
Most people can hear from 20Hz to 20kHz.
Many male voices and a lot of music are below 100Hz so why remove these frequencies?
Consonants of speech very important for understanding what is being said and are from 8kHz to 15kHz so why remove everything above 2.7kHz?
Most people think that an AM radio with a bandwidth of 100Hz to 3kHz sounds awful and a telephone sounds worse. Do you want your hearing aid to sound like that?
the digital pots R1 and R6 (see post #26 for original) expanded the upper end.(post #25)
Need a lower end filter but got the upper end up to 8khz. Will see about getting a second filter for the lower.
Am starting with the "speech filter" that TINA has as an example.
been doing some research over at the Maxium website. They have an amp with audio codec? https://www.electro-tech-online.com/custompdfs/2010/10/Hearing-Aids.pdf
and DSP??
maybe some day after experimenting I can come up with something that works gor everyday use without harming my $$ hearing aids (in the shop etc)
Make your own hearing aid from one of the many Maxim ICs!
I didn't know that there is a hearing aid that down-shifts all audio frequencies so that a person with high frequency loss can hear audio.
It must sound weird but I guess it is better than nothing.
I am not deaf so my hearing works perfectly from 0dB (no sounds) to about 120dB (a motorcycle or diesel truck nearby). I cover my ears when sounds are louder than 90dB continuous or 110dB pulsed.
FM radio stations severely compress their audio so that low level sounds are louder and high level sounds are reduced. It sounds awful and very synthetic. Is that what you want??
Found several schematics that might work but?
Starting with input, then a bandpass filter then an amp.
here are the links with descriptions about each
Started drawing out a schematic but maybe the description would be more helpful.
this first one is kinda of an oddball? Automatic volume control
This phrase is completely wrong: "This circuit passes frequencies in the 300Hz – 3.1kHz range, as present in human speech".
It is only the VOWELS of speech but the very important consonant sounds of S, T, P, Sh, Th and hundreds of other consonants sounds of speech are missing (what did you say?).
Nobody listens to only AEIOU vowels which are not speech. My dogs make those sounds.
Many of your opamps have their input DC voltages at ground so they are rectifiers if they do anything (most inputs don't do anything when they are at ground when there is no negative supply).
R10 and R12 are an attenuator that throws away 91% of the important input signal (from a microphone that has no power?).
Your Jfet circuit has errors. Its source should not be connected to ground. it should have the 4.7k resistor R15 in series with its source to ground and bypassed by the 100uF capacitor C8 as shown in the Fast Peak Limiter project on Rod Elliot's site.
It comes with a (free downloadable) GUI filter designer. You can upload your filters into the chip. The chips aren't cheap-cheap but look at the flexibility and time saved... some have DACs and ADCs included.
I made corrections on the peak cutoff section.
changing the RC componets on the bandpass filter to increase width.
Will get back with schematics and results.
The new version of TINA has somewhere a method to playback WAV files to hear actual changes but havn't figured it out yet.
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